High performance 128 X 128 Si:As and Si:Sb blocked- impurity-band hybrid arrays have been developed for ground- based and airborne astronomy. These devices cover the 5-25 (Si:As) and 15-40 micrometers (Si:Sb) portions of the spectrum. The peak detective quantum efficiencies quantum efficiencies exceed 50 percent for Si:As and 30 percent for Si:Sb. An anti-reflection coat is used to increase responsivity and to reduce internal reflections for the Si:As detectors. The multiplexer yields a linear output response vs. integrated charge. A special design feature of the multiplexer is a changeable nodal capacitance that allows dynamic switching of the well depth between 1.8 X 106 and 1.8 X 107 electrons. The single-sample read noises for the two states are approximately 75 and approximately 760 electrons respectively. These devices have been used successfully to perform astronomical observations in a number of instruments.